Rolling parallel ruler (blade on two notched rollers) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/rolling-parallel-ruler-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 323 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- A straight-edge carries an axle with a roller at each end; the rollers are the same size and fixed to the axle, so as the ruler rolls every point of the blade moves the same distance at right angles to the axle — the blade stays parallel to its starting line.
- The notched rims (24 V-notches, 0.85 mm deep) bite the paper so neither roller slips; the rollers stand 1 mm proud of the underside through openings in the blade. Drawn with a Ø3 × 150 axle, Ø18 × 4 rollers at ±60 mm and a 200 mm blade.
- Brown's No. 323 (rolling parallel ruler); the navigator's parallel rule.
- Parts (each has its own page): rolling-ruler-blade-200-d18, notched-roller-d18x4-b3, linear-shafts-h6.
- Brown's movement No. 323 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
blade  200 × 24 × 6 mm
rollers  2 × Ø18 × 4, notched
axle  Ø3 × 150 (linear shaft)
roller spacing  120 mm

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Henry T. Brown (1868, public domain): Five Hundred and Seven Mechanical Movements — scan on archive.org — web — Publisher's page; dimensions are facts — https://archive.org/details/fivehundredseven00browiala
- 507movements.com: Brown's movement No. 323: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_323.html

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/rolling-parallel-ruler-mechanism/index.json
API: https://xemstudio.com/api/geometry?object=rolling-parallel-ruler-mechanism